The main objectives of this project are to understand the functions of the visual system of higher vertebrates, using physiologic and anatomic techniques. Our main approach, which is neurophysiologic, is to record from the visual pathway, using extracellular single unit techniques, comparing responses to retinal stimulation at different stages, from retina to cortex. Parallel with this we are studying the anatomy of the visual system, using a variety of techniques, especially experimental silver-degeneration (the Nauta method and its modifications) and electron microscopy. A major part of our effort is also devoted to a study of the effects of visual deprivation and strabismus in cat and monkey, at various ages. Bibliographic references: LeVay, S., Hubel, D.H., & Wiesel, T.N. (1975) The Pattern of Ocular Dominance Columns in Macaque Visual Cortex Revealed by a Reduced Silver Stain. J. Comp. Neur., 159:449-576. Drager, Ursula C. and Hubel, D.H. (1975) Physiology of visual cells in mouse superior colliculus and correlation with somatosensory and auditory input. Nature, 253, 203-204.